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Blood. 2007 Feb 15;109(4):1568-73. Epub 2006 Oct 5.

L-arginine availability regulates T-lymphocyte cell-cycle progression.

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Tumor Immunology Program, Stanley S. Scott Cancer Center, Lousiana State University Health Sciences Center, Department of Pediatrics, New Orleans 70112, USA.


L-arginine (L-Arg) plays a central role in several biologic systems including the regulation of T-cell function. L-Arg depletion by myeloid-derived suppressor cells producing arginase I is seen in patients with cancer inducing T-cell anergy. We studied how L-Arg starvation could regulate T-cell-cycle progression. Stimulated T cells cultured in the absence of L-Arg are arrested in the G0-G1phase of the cell cycle. This was associated with an inability of T cells to up-regulate cyclin D3 and cyclin-dependent kinase 4 (cdk4), but not cdk6, resulting in an impaired downstream signaling with a decreased phosphorylation of Rb protein and a low expression and binding of E2F1. Silencing of cyclin D3 reproduced the cell cycle arrest caused by L-Arg starvation. The regulation of cyclin D3 and cdk4 by L-Arg starvation occurs at transcriptional and posttranscriptional levels. Signaling through GCN2 kinase is triggered during amino acid starvation. Experiments demonstrated that T cells from GCN2 knock-out mice did not show a decreased proliferation and were able to up-regulate cyclin D3 when cultured in the absence of L-Arg. These results contribute to the understanding of a central mechanism by which cancer and other diseases characterized by high arginase I production may cause T-cell dysfunction.

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